Add documentation for conv2()/plan_brfft()
Added doc/UNDOCUMENTED.rst, functions for generating

This collects all known undocumented modules and functions and
puts them in doc/UNDOCUMENTED.rst, using standard function and
method templates so they can be easily filled in and copied to
the correct .rst file in doc/stdlib.

This file can be regenerated with

```julia
cd("$JULIA_HOME/../../doc")
import DocCheck
DocCheck.gen_undocumented_template()
```
fix #3909
Merge pull request #3912 from kmsquire/undocumented_updates

Added doc/UNDOCUMENTED.rst, functions for generating
Merge pull request #3913 from JuliaLang/sf/dspdocs

Add documentation for conv2()/plan_brfft()
base/Makefile: fix FreeBSD date bug; replace $(CC -E) -> $(CPP)
Update openblas to v0.2.8-rc1 for wider testing.
bump openblas from v0.2.8-rc1 -> v0.2.8
Remove deprecated addprocs_sge entry. The documentation did say
that the function was deprecated, but we are not doing this elsewhere -
hence deleting this entry.
Merge branch 'master' of github.com:JuliaLang/julia into jb/newvars